Expressing gratitude for your boss' feedback — even if it's negative — can make them act nicer toward you, according to a 2011 study from the University of Southern California.
In one experiment, about 200 undergrads were told that they had been assigned a partner and were supposed to review a draft of instructions the partner had written about how to assemble parts of equipment. (In reality, there was no partner and the instructions had been written by the experimenter.)
Some participants were told they were the supervisor in this relationship; others were told they were the subordinate. In addition, all participants took a pretend test of their abilities and some were told they weren't that competent.
When the experimenter returned notes from the "partners," some said, "I just wanted to let you know that I received your feedback on my draft." Others said the same thing, along with, "Thank you so much! I am really grateful."
As it turns out, participants in the supervisor position who'd been told they weren't that competent were nicer when their partners were grateful.
When their partners weren't grateful, the supervisors whose competence had been threatened were more likely to respond by denigrating those partners, saying they were unintelligent, incapable, and incompetent. You might say gratitude prevented the threatened supervisors from acting like jerks.